Wrong Absolute Altitude
I recently did a mission where the absolute altitude was off my some margin. Should be approx 70m but came out at 140m
The reative was correct at 50m
Looking back the only different things
1 - Couple of 1080 errors when starting up but I just try again and it works (doubtful this is the issue!)
2 - During battery changes etc I manually fly the drone back and forth to me so it does it faster than the auto RTM
3 - The mission I flew is one Ive done a few times but I realised afterwards that I had picked up a previously aborted mission. I dont recall aborting one but only realised afterward as the starting point was an old one
Any ideas if any of the above could cause teh altitude issue and if not what else could ?
I had issues in the past but that was when used to start with DJI Fly before flicking into Dronelink.
Thanks
Comments
10 comments
Bryn
I think this is your problem. The altitude is calculated using barometric pressure. That can change significantly if not run on the same day.
If you took off from a different location and the mission was set to calculate the altitude from a previous location, that can make a big difference. As Barry stated, the drone only has a barometric altimeter, which measures altitude relative to where the drone takes off, and even that drifts over time as the pressure changes during the flight.
Thank you both and I will run a couple of tests today
Just did a small test with a brand new mission and it ran and completed okay and similar issues - absolute altitude coing in 125 which is off.
Only anomoly was the view on he phone of the photos being taken was that of somewhere I had been 20 mins before . The map was in the right locaton though
Bryn
Can you share the mission?
And, trying to be clear, what do you mean by absolute altitude? Typically, altitude is above ground, meaning if you took off 125' above the site, with an altitude of 50', then all altitudes would be at 175' above the site.
Here is the mission
https://app.dronelink.com/bryn-morgan/test/plan/E9i05vqmxDo6xxJWBCVn
I get absolute and relative altitudes when load into DroneDeploy who I use toe stitch them together. Click on any of the 43 images and you will see they are all about 50m relative (correct as thats the mission height) but the absolute is about 130 which should be about 70
https://www.dronedeploy.com/app2/sites/64c8f340d2acbe151bea912b/maps/64c8f362d2acbe151bea912d?jwt_token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpZCI6IjY0YzhmMzZiMzUwZWM0MmEzNjZjZTQ5NCIsInR5cGUiOiJQdWJsaWNTaGFyZVYyIiwiYWNjZXNzX3R5cGUiOiJwbGFuIn0.hA3PYi8rqkN638kfHR8LaLvapxQq7wRDQ3hyVYuqux4A3gZfLA06ahAMmX310XjplgE5iXlsmStErehXk1-22A
I am guessing the absolute altitude shown in DD is the GPS altitude (MSL) that DJI saves in the metadata of the image. DL has no control over this behavior or how accurate it is.
I did some just directly in DJI Fly and they were out too by the same amounts
The absolute altitude is approx above sea level apparently.
So I know its wrong on the basis I live on the coast. They have generally been correct until recently
Most odd and frustrating
When was the last time you ran calibrations on the drone
I agree with Martin. I’d go through everything, firmware, calibrations and check again. Regardless of where your flying, at sea level or at 5,000 feet like me, the altitude indicated in the app is always ATL (Above Take-off Location). If not indicating properly with the DJI app then it’s a drone issue.
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